FIG. 1 depicts a conventional video conferencing system 10. A camera 12 of the video conferencing system 10 has a charge-coupled device or CCD 13 on which an image is incident. Cameras of the type illustrated in FIG. 1 called ColorCam are available from Connectix.TM. a company located in Mountain View, Calif. The CCD 13 outputs a still or moving picture video signal representing the image or images incident thereon to an analog to digital converter (ADC) 15. The ADC 15 illustratively outputs an RGB format digital video signal. The digital video signal is conveyed by a cable 16 to a parallel printer port 18 of a computer system 20. The picture data received from the parallel printer port 18 is provided to a frame capture I/O expansion card 19 via a proprietary internal cable 23. The I/O expansion card 19 has a buffer for receiving frames of the digital video signals for communication via I/O expansion bus 22 to an I/O bridge 24. The I/O bridge 24 retransmits the video data thus received via a system bus 26 to a processor 28. Once at the processor 28, the bit rate of the video signal may be adjusted in a number of ways. For instance, the resolution or frame rate may be decreased. Alternatively, the video may be encoded according to one of a number of encoding standards including ITU's (International Telecommunications Union) H.261, H.262, or H.263, ISO/IEC's MPEG-1, MPEG-2, JPEG, or motion JPEG, etc. After reducing the bit rate of the video signal sufficiently, the bit rate reduced video signal may be outputted from the processor 28, via system bus 26, I/O bridge 24 and I/O expansion bus 22 to a modem 30. The modem 30 transmits the bit reduced video signal to a remote video conferencing system 10' via a network 32, such as a public telephone network, local area network (LAN), metropolitan area network (MAN), wide area network (WAN), etc. The bit rate reduced video signal is received at a like modem 30 and communicated to a like processor 28 where it is restored (decompressed, spatially and/or temporally interpolated, etc). The restored video signal is then outputted to a graphics adapter 33 and displayed on a display monitor 34. Alternatively, the restoration can be performed on the graphics adapter 33 using specialized hardware.
A conventional personal computer system 20 generally only has two standard ports, namely, a parallel port and a serial port. The parallel port is typically used for outputting data to a printer and can output data at a maximum 100 Kbyte/sec burst transfer rate using a handshake protocol. The serial port, on the other hand, is typically connected to an input device, such as a mouse, or a modem and can typically only sustain a 115.2 Kbit/sec transfer rate (e.g., using a 16550 UART). As noted above, the camera 12 can connect to a standardized connector at the printer port 18. This enables the camera 12 to be used with different platforms (e.g., different computer systems). However, to do so, the printer must be disconnected from the parallel port 18 as the parallel port 18 can only support data transfers between the computer system 20 and one other peripheral device (pursuant to its handshake protocol). This is disadvantageous. Another disadvantage of the computer system 20 is that the computer system housing (represented by 21) must be opened to install the frame capture I/O expansion card 19 and to manually connected the proprietary connector 23 between the parallel port 18 and the frame capture I/O expansion card 19. Thus, a novice user may find it difficult to install and to configure the camera 12. Moreover, for many systems 20, the warranty on the computer is voided if the computer housing 21 is opened by the user.
The camera 12 is well suited for non-real-time still picture capture. In capturing a still image, there is no requirement to transfer the data of the still picture from the camera 12 to the computer system 20 (or to, for example, another video conferencing system 10') in real time. A raw RGB signal for a 600.times.800 pixel display screen contains (800.times.600 pixels).multidot.24 bits/pixel=11,520,000 bits. At the maximum 100 Kbyte/sec burst transfer rate of the parallel port 18, the transfer of one still image from the camera 12 to the computer system 20 takes over 14 seconds (without adding in the overhead of the printer port 18 handshake protocol or any other bus arbitration of transfer latency of the computer system 20). Moreover, to transfer such information via modem 30 connected to an ordinary telephone network (which can have up to a 28.8 Kbit/sec transfer rate) would require 400 sec. This presents a problem for real time video communication, such as, video conferencing, in which moving pictures must be captured, transferred, and displayed in real time.
It is possible to program processor 128 to perform a limited amount of real time video capture for transfer via the network 32 using the video conferencing system 10. The problem is that only a limited amount of data can be transferred from the camera 12 via the printer port 18 to the frame capture I/O expansion card 19 due to the limited bandwidth of the printer port 18. As such, the resolution of the image must be drastically reduced to no larger than 128.times.96 pixels (for a black and white image) which results in approximately a 2".times.2" picture on a normal display monitor 34. The frame rate is reduced to approximately 7 frames per second (using a frame dropping technique). (Note that (128.times.96).multidot.(8 bits/pixel).multidot.(7 frames/second)=688,128 bits/sec which is slightly less than the 100 kbyte sec maximum bust transfer rate of the parallel port 18.) Moreover, the image quality is severely deteriorated; ghost shadows are perceptibly present in the restored image, and the image breaks up whenever there is a large degree of motion in the picture.
FIG. 2 shows a modified video conferencing system 50. In this system 50, the camera 12 produces either an analog signal or a digital RGB signal carried by cable 16. The signal is received at a video processing I/O expansion card 52 that is inserted into an available slot 54 on the I/O expansion bus 22. The I/O expansion card 52 can have a frame capture circuit 55, an ADC 56 and a bit rate reduction circuit 58 (e.g., a video compressor or frame rate/resolution reduction circuit). Examples of such circuits include the Vision Controller Processor (VCP.TM.) available from 8.times.8.TM., a company located in Santa Clara, Calif., and APV-3.TM. available from Lucent.TM., a company located in Murray Hill, N.J. The video signal is received at the video bit rate reduction circuit 58 on the video card 52 and is bit rate reduced thereat. The bit rate reduced video signal is then transmitted on the I/O expansion bus 22 to the processor 28 and/or to the modem 30.
The video conferencing system 50 can provide an adequate frame rate and resolution video signal at a bit rate which can be transmitted via the modem 30. The problem with the system 50 is that the computer housing 60 must still be opened to install the video processing I/O expansion card 52. Second, the cable 16 connects to a non-standardized connector 62 on the video processing I/O expansion card 52. This reduces the interchange-ability of video cameras 12 from platform to platform.
FIG. 3 shows an IEEE 1394 compliant camcorder 90 soon to be available from Sony.TM. a company located in Tokyo, Japan. The IEEE 1394 standard is a new standard for compression, storage and transfer of consumer and professional use digital video signals. The camcorder 90 includes a CCD 91, an ADC 92, a motion JPEG compressor 93 and an IEEE 1394 interface 94. A video signal outputted from the CCD 91 is converted to digital form in ADC 92 and then compressed in JPEG compressor 93. The compressed video signal is then formatted according to the IEEE 1394 standard and outputted to a bus using interface 94. The IEEE 1394 bus is a 400 Mbit/sec bus for which no computer interface is yet available. Moreover, the IEEE 1394 bus is designed for transfer of video signals only--no specific provisions are provided for supporting non-video "bursty" data transfers.
Another problem specific to both the video conferencing system 10 and video conferencing system 50 pertains to properly setting up the system on each end of the communication. For instance, there is no guarantee that both the video conferencing system 10 and the video conferencing system 10' will use the same camera, the same frame captured board or technique, or have the same coding/decoding capabilities. Even when both video conferencing systems on each end of the communication are identical, a skilled operator is necessary to properly install the hardware and software and also to configure the software and hardware each session. In particular, the operator must select the correct software drivers, select compatible bit rate reduction methodologies, i.e., the correct encoding and decoding technique, options and parameters, the correct resolution, the correct frame rate, etc. In the case where each end of the communication need not have an identical video conferencing system 10 or 10' each operator must be provided with preliminary information on the capabilities of the system at the other end and must somehow agree to select the correct frame rate, resolution, encoding/decoding technique parameters and options. This makes it difficult for a novice user to establish an interactive video teleconference with an arbitrary user.
It is object of the present invention to overcome the disadvantages of the conventional cameras. In particular, it is object to provide a video conferencing system in which the camera can be connected to a standard computer port without opening the computer housing, yet have sufficient resolution and fidelity to enable interactive communication of moving pictures. It is also an object to provide other kinds of video peripherals which can output and receive video signals in a simple "plug and play" fashion. It is furthermore an object to provide a video conferencing system that can arbitrate with a like far end video conferencing system and automatically configure itself on a session by session basis.